Project summary Longevity has increased dramatically in the U.S. since the last century, and the prolonged life expectancy has prompted discernible growth in age-related diseases. Longevity and healthy aging have become two primary goals of public health, and it is imperative to better understand how modifiable lifestyle factors affect both outcomes across adulthood from a life course perspective. However, to date, few studies have addressed these questions, in part due to the lack of appropriate statistical methods and the scarcity of available longitudinal data. Our Specific Aims are: 1) To develop a novel mixture model for trajectory analysis with high flexibility using a modified expectation- maximization (EM) algorithm based on generalized additive mixed model (GAMM); and 2) To examine associations of trajectories of lifestyle factors and trajectories of difference in lifestyle factors every 2-4 years from early adulthood to old age (approximate 30-75 years) with healthy aging and longevity using our proposed model in the Nurses? Health Study (NHS) and the Health Professional Follow-up Study (HPFS). The NHS and the HPFS are excellent resources for the proposed study because of 1) large sample size; 2) 30-40 years follow-up; 3) multiple updated and validated lifestyle data. Our proposed method will strongly impact the life course research in health and social sciences by introducing a novel model of high flexibility that overcomes limitations of existing methods. Our study will fill the substantial knowledge gap on how change of lifestyle factors associate with healthy aging and longevity across adulthood, and identify potential critical periods (young adulthood, middle age, old age) to best achieve both outcomes. Our study will be of crucial